1. Field of the Invention
The present invention relates to a method, computer program and system for designing a wiring harness assembling table and a related technique.
2. Description of the Related Art
Wiring harnesses are used as electric wiring in automotive vehicles and electric appliances. A wiring harness is produced by first making a 3D wiring design of the wiring harness based on mount positions of various parts in the automotive vehicle, electrical appliance or like wire layout object. The wiring harness then is drafted on a two-dimensional (2D) drawing sheet based on the result of the 3D wiring design. FIG. 14 shows a typical assembly board 1 for assembling the wiring harness. Supporting jigs 2 are mounted at selected locations on the assembly board 1 based on the 2D drawing of the wiring harness. Wires then are supported on the jigs 2 and are bundled with resin tape or the like to produce a wiring harness 3.
The wiring harness design typically is evaluated by generating 2D drawings of the wiring harness and the vehicle or appliance for which the wiring harness is being designed. These 2D drawings typically are made by a design assisting system, such as a CAD. A designer checks the drawings and points out problems. The acceptability of this method varies widely depending on the skill of the designer and it is difficult to establish a uniform standards.
Alternatively, a trial wiring harness 3 is produced and is actually laid in an automotive vehicle, electric appliance or other such wire layout object 4, as shown in FIG. 15. The acceptability of the wiring harness is investigated by checking whether the trial wiring harness 3 can be laid properly in the wire layout object 4 so that connectors 5 and wires are in proper locations.
This latter method points out the three-dimensional problems. However, a wiring harness assembling process generally depends mostly on manual operations. Accordingly, the production of the trial product is a labor-intensive operation and requires huge expenditures of labor and time.
A conventional development method for a wiring harness is shown in the flow chart of FIG. 23, and includes drafting a preliminary drawing in Step T1 based on a summary of an object in which a wiring harness is to be used. Design and development operations then are performed in Step T2.
Trial products are produced at Step T3 based on the design developed in Step T2. The production of trial products in Step T3 requires jigs 2 and other parts for the actual wiring harness to be arranged on an assembling table, as shown in FIG. 14. A skilled worker or a research engineer then assembles an actual wiring harness 3 as a trial product.
The design developed in Step T2 and the trial product produced in Step T3 are assessed based on several factors, including: an error in certain design rules for the wiring harness 3, such as insufficient dimensions or exertion of an unnatural load at a mount angle; the possibility of human errors; the presence of a mutual hardware interference for the jigs 2; and difficulties during the assembling operation. Factors that adversely affect productivity and/or quality are pointed out, and plans that could remove such adverse factors are studied. The results of the trial product investigation eventually are reflected on the content of the trial product design. Trial products usually are produced several times in Step T3. A production preparation stage (Step T4) and a mass production stage (Step T5) eventually are entered.
Research engineers play a key role at the trial production stage of a wiring harness in an effort to design improved operation steps for the subsequent mass production stage. Actual trial products are produced and trial product operations are inspected in an effort to improve the assembly of the wiring harness by human hands. Operations that are difficult and/or that have low operability are addressed early in the trial production stage in an effort to develop an improvement plan that will obtain high productivity at the mass production stage. The improvement plan frequently is associated with an improved design of the wiring harness, and the improvement plan is drafted with a view to giving improvement feedback to the design at an early stage.
The preparation for the trial production is illustrated in the flow chart of FIG. 46. In particular, a wiring harness is designed in Step S201 and research engineers draft a full-size drawing in Step S202. The research engineers produce and study production planning information in Step S203, such as: an initial schedule and the number of harnesses that will be produced; factory information, including the type of existing facilities, manufacturing system standards and producing abilities at factory facilities. This step is carried out while looking at the full-size drawing. Thereafter, separate designing of first subassemblies is drafted in Step S204, and a specific mass production line is designed in Step S205.
As shown in FIG. 47, the subassemblies (subassemblies 1, 2, . . . n in FIG. 48) designed in Step S204 are intermediate products produced at an intermediate stage as small-size components of a wiring harness 2 (final harness product in FIG. 48). The subassemblies 1 normally are designed for sections of automotive vehicles, such as engines and doors. The final product of the wiring harness 2 is an assembly of these subassemblies 1 and is an aggregate of many kinds of parts 3, including, wires (e.g. 100 to 150 wires) and covering parts (e.g. dozens to several hundred covering parts) such as protectors, covers and tapes. The wires and the covering parts are cut and connected, as indicated schematically by the numeral 4. The parts 3 are assembled most efficiently by first producing small-size minor subassemblies 1 with machines 5 or by assembling by human hands 6. The subassemblies 1 are arranged and combined successively on a harness assembling table. Wires 7 and parts 8 that are not included in the subassemblies 1 in FIGS. 47 and 48 are independent parts 9 that are connected independently and separately from the subassemblies 1 to form the final wiring harness 2.
A procedure for the separate designing of the subassembly in Step S204 is shown in FIG. 49. In particular, harness design information is obtained in Step S211 from a production designing system (HIS) as a software program of a computer. Wires and connectors for the wiring harness are outputted and are converted into a matrix table as shown in FIG. 50 based on the harness design information in Step S212. Forms, such as a subassembly 1a in FIG. 51A and a subassembly 1b in FIG. 51B (Step S213), are grouped and sampled repeatedly while the outputted matrix table is observed. The separate operations are repeated to optimize matters, such as: whether the subassemblies have sizes easy to handle by workers; whether a terminal insertion rate is at maximum; and whether the wire laying operation can be performed smoothly. The division of the subassemblies is completed when these operations are ended. However, the designing of the subassemblies (Step S204) using the matrix table (see Step S212) is performed on paper, and the result of the designing needs to be verified using an actual product.
When the separate designing of the subassemblies of Step S204 is completed (Step S214 in FIG. 49), the parts 3 actually are prepared as shown in FIG. 47 and the subassemblies 1 actually are produced. Further, a harness assembling table to assemble an actual wiring harness is manufactured in accordance with the contents of the full-size design (see Step S202 in FIG. 46) to investigate an assembling operation.
An order of using the respective subassemblies 1 and an assembling procedure on the harness assembling table are determined beforehand in accordance with industrial engineering theory. A research engineer then performs an assembly operation in accordance with the assembling procedure. Operability is inspected and improved, with great importance placed on matters to be investigated in terms of a wire laying operability and an operation procedure as listed in TABLE-1 below.
TABLE 1MATTERSTO BECONFIRMATIONINVESTIGATEDPOINTSREMEDIESWire LayingAny unnecessaryMake subassembliesOperabilityoperation when ansmaller or change theoperator handlesforms thereof to increase asubassemblies?first insertion rateSubassemblies can beCorrect the designs of thesmoothly laid in onesubassemblies to conformdirection (from leftto a layout of the boardside to right sideon board)?Many overlapping wireReconsider and optimizelaying operations?the forms of all thesubassembliesOperationAny unnecessaryReconsider and changeprocedureoperation betweenthe operation procedureoperation steps?
Confirmation points concerning the wire laying operability include: whether there is any unnecessary operation while a worker is handling the subassemblies 1; whether the wires can be laid in one direction, i.e. from left to right on the harness assembling table; and whether there are many overlapping wire laying operations. Further, investigation is made as to whether there is any unnecessary operation between the operation steps. Remedies for the identified problems shown in the column of “Remedies” in TABLE-1 are studied.
Improved operability can be made by repeatedly producing actual trial products. The remedies proposed at this time include those related to the divided forms of the subassemblies and those accompanied by design changes. A design change plan is put into shape immediately and feedback is given to the design department for improvements.
The aforementioned process is carried out to prepare a production environment for actual products. The actual products then are assembled and productivity- and quality-related hindering factors at the trial production stage are pointed out. An improvement requirement is presented to a client or an internal design department so that the result of the investigation can be reflected on a next trial production. Thus, many operation steps and a long time (about 1 month) are required to complete and evaluate one trial product.
Many trial products are produced and evaluated despite a growing demand from the client to shorten the development period. Therefore, it has become difficult to have sufficient time and to perform a sufficient number of operation steps. As a result, the trial production process often is delayed and inspection precision is reduced. This results in problems being carried over to a next trial production process or a reduction in productivity and quality at the mass production stage.
Accordingly, an object of the present invention is to enable an efficient wire layout investigation by virtually investigating a wire layout for a wiring harness design.